Optimization of Practical Feeds in Ti La Pia Farming- Israel

7/31/2019 Optimization of Practical Feeds in Ti La Pia Farming- Israel

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Optimization of Practical Feeds in Tilapia Farming

1. Introduction

Tilapia are grown in inland aquaculture in Israel in various kinds of facilities andproduction strategies. Much of the tilapia is grown extensively in poly-culture butmore and more intensive monoculture systems are being used where the pelletedfeed is the only source of energy and nutrients. Thus, successful fish culture dependsupon the provision of diets containing adequate levels of energy and nutrients tosustain the best possible growth. In addition there is a need to prevent feed waste, asthis is costly to the farmer and problematic for the environment.This study is a joined project of the National Center of Mariculture and the IntensiveFish Culture Station at Ginossar where the actual trials took place. The methodologyused for this kind of study has been successfully applied at NCM to developcommercial feeds for fish like the gilthead seabream, European seabass and whitegrouper.

The general assumption is that the energy and protein requirements of a growing fishare the sum of the needs for maintenance plus growth. The requirement formaintenance is mainly a function of the size of the fish and water temperature, and is

proportional to the metabolic body weight in the form of a body weight (kg)b, wherea is a constant, characteristic of a certain fish species at a set temperature and b isthe exponent of the metabolic body weight which in fish is b = 0.80.The requirement for growth is dependent on the amount and the composition of theweight gain, including the cost of energy to deposit the new growth.

Daily energy requirements can therefore be quantified as:

Digestible energy needs (kJ) = a body weight (kg)0.80+ cenergy gain (kJ)

Where c = cost of production in units of dietary energy to deposit energy as growth.

The same approach is used for the quantification of protein, except for the use of adifferent exponent of b = 0.70 for metabolic body weight.

Digestible protein needs (g) = a body weight (kg)0.70 + cprotein gain (g)

Where c = cost of production in units of dietary protein to deposit protein as growth.

The significance of this approach is, that protein and energy needs are expressedprimarily in terms of absolute demand per fish body mass and anticipated weightgain. As energy and protein consumption is the product of feed intake and feedcomposition the voluntary maximum feed intake as well as the composition of thefeed have to be considered. Feeds can then be formulated and feeding tablesestablished which are based on daily requirements for energy and protein dependenton anticipated growth.


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2. Material and Methods

2.1 Maintenance Requirement

To determine the maintenance requirement and efficiency for growth tilapia were fedincreasing levels of a feed with a known digestible energy (DE) and digestible proteincontent (DP). Feeding levels included zero groups (no feed) up to maximumvoluntary intake and energy and protein gain were determined by comparativecarcass analyses.Two growth trials with tilapia of 115g and 300g initial weight were performed duringthe summer 2005 during which the water temperature ranged between 27 - 280C.Tilapia were graded and 1m3 tanks each stocked with 40 fish. The feed used in thetrials was formulated from fish meal, wheat meal and fish oil, to contain 40% proteinand 9% lipid (Table 1). Feeds were produced as floating pellets by the Zemach feedmeal. Daily feed amounts were estimated initially as zero, low, high and maximumrelative to body weight. Feed was given once a day at the low feeding levelincreasing to up to 4 times daily at the high feeding level to ensure equal distribution

of the food pellets among the fish.

Table 1: Formulation and composition of diet

Diet

Ingredients (g / kg)Fish meal 309Soybean meal 47% 252Corn gluten 80Wheat meal 295Fish oil 58Vitamin mix 6

Analysis ( per kg)Dry matter (DM), g 930Crude protein, g 389Crude lipid, g 94.3Ash, g 75.0Gross energy, MJ 20.02Digestible energy (DE)*, MJ 15.02Digestible protein (DP)*, g 328

* According to digestibility values determined for tilapia (Sklan et al. 2004)

2.2 Growth and Feed Intake

To asses the growth potential and the feed intake of tilapia at various temperaturesadditional growth trials were performed in the Ginossar experimental unit. Thissystem is equipped to keep constant temperatures of 22, 24, 26 and 290C in paralleltanks throughout the 112 day trial. 70 Tilapia of 25g initially were stocked in 1m 3tanks, fish were hand fed and feed was given four times a day, any left over feed wascollected and weighed. The feed used in the trials was the same diet as described inTable 1. The daily feed intake and growth was monitored at each temperature bymonthly weighing.Furthermore, to determine the effect of temperature on energy and proteinmaintenance requirements, tilapia of various sizes were stocked alongside the

growth trials for about 30 days without being fed. Fasting fish underwent the sametemperature regime (220C, 240C, 260C and 290C) as the fed fish.


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2.3 Composition of Weight Gain

The composition of the weight gain is an additional factor determining thesubsequent energy and protein requirement. To determine the body composition oftilapia of different sizes along the growth cycle, fish were sampled at the start and theend of the growth trials as well as each month at weighing time.

3. Results

3.1 Requirement for Maintenance

The results of the trials where tilapia were fed increasing feed amounts are presentedin the following tables and figures. Feed intake, growth performance and FCR areshown in Table 2.

Table 2: Growth parameter of tilapia fed at increasing feeding levels after 52 (or 32)days of experiment.

Treatment Weightinitial g

Weightfinal g

Gaing / day

Feedratio %

FCR Daysof growth

Tilapia of 100gStarvation 114 101 -0.39 0.00 32Maintain 110 138 0.54 0.57 1.32 52Low 105 169 1.25 1.07 1.14 52Medium 113 196 1.59 1.41 1.32 52Maximum 112 205 1.80 1.68 1.41 52

Tilapia of 300gStarvation 311 279 -1 .01 0.00 32Maintain 309 337 0.53 0.36 2.18 52Low 315 377 1.35 0.68 1.76 52Medium 312 416 2.00 0.88 1.59 52Maximum 306 437 2.52 1.13 1.63 52

The comparative slaughter technique was used to determine energy and protein gainfor the different groups of tilapia at each feeding level. Feeding tilapia graded levelsof digestible energy (DE) resulted in a linear response (Figure 1). The relationshipbetween daily DE intake (x) and energy gain (y) on a metabolic weight basis of kg0.80can be described by the following linear equation:

y = - 31.63 + 0.60x r2 = 0.96 (1)


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DE fed (kJ / kg0.80

/ day)

0 20 40 60 80 100 120 140 160 180 200

Energygain(kJ/kg

0.80 /d

ay)

-60

-40

-20

0

20

40

60

80

100 g Tilapia

300 g Tilapia

Figure1. Daily energy retention per unit metabolic weight of kg0.80 in tilapia of two sizegroupsfed increasing levels of DE.

Maintenance requirement (DEmaint) can be found where energy gain equals zero (y =0) and the efficiency of DE for growth is defined by the slope of the line which

amounts to 0.60 (equation 1). The required energy intake is calculated as DEmaint =52.72 kJ BW (kg) 0.80. This can be considered the daily maintenance requirementfor tilapia at 270C.

The relationship between dietary DP intake and protein retained in g / BW (kg) 0.70was linear as well (Figure 2) and the relationship is described by the followingequation:

y = - 0.33 + 0.48x r2 = 0.95 (2)

In the case of protein the efficiency of utilization can again be defined by the slope ofthe line and amounts to 0.48 and the daily maintenance requirement for protein can

be calculated as DPmaint = 0.69g BW (kg)0.70.


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DP fed (g / kg0.70

/ day)

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Proteingain(g/kg

0.70/d

ay)

-0.50

0.00

0.50

1.00

1.50

100 g Tilapia

300 g Tilapia

Figure 2. Daily protein retention per unit metabolic body weight of kg0.70 in tilapia oftwo size groups fed increasing levels of DP.

To estimate the maintenance requirement at increasing water temperatures, thesame relationships between DE intake and energy gain were established fortemperatures between 220C to 290C. Figure 3 depicts the relationship between dailyDE intake (x) and energy gain (y) on a metabolic weight basis of kg0.80

DE fed (kJ / kg0.80

/ day)

0 50 100 150 200 250

Energygain

(kJ/kg

0.80/

day)

-80

-60

-40

-20

0

20

40

60

80

100

120

140

220C

240C

260C

290C

Figure 3: Daily energy retention per unit metabolic body weight of kg0.80

of fed andnon fed tilapia fed at various water temperatures.


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The relationship between daily DE intake (x) and energy gain (y) on a metabolicweight basis of kg0.80 can be described by the linear equations following below. Inaddition the maintenance requirement - DEmaint - where energy gain y = 0 can bedetermined at increasing temperatures:

At 220C y = - 21.19 + 0.54x DEmaint = 39.24 kJ (kg)0.80 (3)




The same data set can also be used to establish the relationship between proteinintake (x) and protein gain (y) referring to a metabolic body weight of kg0.70. Thisdefines the requirement of protein for maintenance and the cost in terms of dietaryprotein needed to deposit protein as growth.

At 220C y = - 0.17 + 0.40x DPmaint = 0.43 g (kg)0.70 (7)At 240C y = - 0.25 + 0.46x DPmaint = 0.54 g (kg)

0.70 (8)

At 260C y = - 0.30 + 0.48x DPmaint = 0.62 g (kg)0.70 (9)

At 290C y = - 0.42 + 0.53x DPmaint = 0.79 g (kg)0.70 (10)

DP fed (g / kg0.70

/ day

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Proteingain(g/kg

0.70 /day)

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

220C

240C

26

0

C29

0C

Figure 4. Daily protein retention per unit metabolic body weight of kg0.70 of fed andnon fed tilapia fed at various water temperatures.

The efficiency of energy utilization for growth above maintenance or in other wordsthe cost to produce new growth seems to increase with increasing temperatures.This is quite unusual and here tilapia might behave differently from other fish specieswhere efficiency above maintenance is independent from feed intake and


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temperature. One of the explanations could be, the digestibility especially of thecarbohydrate fraction would decrease at lower temperatures. Until further trials willconfirm this assumption an average slope of 0.62 for energy utilization and 0.47 forprotein utilization is determined and used in further calculations.

In the range between 22 to 290C the relationship between maintenance requirementboth for energy and protein and temperature is linear and can be well described byfollowing equations:

Maintenance requirement for energy in kJ/day/fish:

DEmaint = ( - 39.02 + 3.48 T0C ) (kg)0.80 r2 = 0.92 (11)

Maintenance requirement for protein in g/day/fish

DPmaint = (- 0.634 + 0.048 T0C) (kg) 0.70 r2 = 0.88 (12)

3.2 Requirement for Growth

3.2.1 Growth prediction and voluntary feed intake

A necessity for estimating the feed requirement is a prediction of the maximumgrowth potential of tilapia. In Tables 3 through 6 feed intakes, growth performanceand FCR for the tilapia grown at the different temperatures are shown.

Table 3: Growth performance of tilapia first segment 35 days


Weightfinal g

Gaing / day

Feedratio %

FCR

220C 30.14 1.54

48.33 1.58

0.52 0.02

2.01 0.10

1.48 0.03

240C 29.64

1.62

56.79

1.51

078

0.05

2.45

0.18

1.30

0.01260C 29.93

1.11

63.34

0.88

0.95

0.06

2.61

0.14

1.19

0.03290C 28.83

1.08

67.33

1.97

1.10

0.04

2.98

0.10

1.190.03

Table 4: Growth performance of tilapia second segment 29 days


Weightfinal g

Gaing / day

Feedratio %

FCR

220C 48.03

1.74

64.52

1.72

0.57

0.05

1.55

0.12

1.53

0.14240C 55.98

0.76

80.63

3.72

0.85

0.11

1.74

0.06

1.38

0.10260C 63.02

1.09

105.42

10.48

1.46

0.35

2.02

0.11

1.16

0.17290C 67.41

2.37

117.41

0.57

1.72

0.08

2.19

0.12

1.13

0.08


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Table 5: Growth performance of tilapia third segment 32 days


Weightfinal g

Gaing / day

Feedratio %

FCR

220C 65.61

2.32

88.19

2.87

0.71

0.08

1.43

0.20

1.54

0.09240C 81.34

5.04

123.71

12.36

1.32

0.27

1.66

0.16

1.28

0.13260C 105.18

12.83

167.85

14.33

1.96

0.13

1.83

0.15

1.24

0.14290C 117.22

1.86

195.88

6.68

2.46

0.26

1.91

0.18

1.18

0.01

Table 6: Growth performance of tilapia fourth segment - 16 days


Weightfinal g

Gaing / day

Feedratio %

FCR

220C 90.36

3.70

102.17

7.41

0.74

0.16

1.66

0.14

2.31

0.56240C 124.03

14.02

150.40

13.42

1.65

0.06

1.64

0.03

1.36

0.18260C 165.49

16.83

198.28

22.71

2.050.37

1.56

0.15

1.40

0.24290C 195.23

6.07

239.18

0.66

2.75

0.41

1.55

0.18

1.25

0.32

From this data set absolute weight gain as well as feed intake per day was calculated

for the period between two successive weighings. The corresponding body weight forthe period was the geometric weight of the fish during that period. Thus together withthe growth data from Table 2 a data set of daily weight gain as well as daily feedintake at different water temperatures has been obtained with tilapia. Daily weightgain in relation to fish size ranging between 20 and 400g at various temperatures arepresented in Figure 5.


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Fish weight (g)

0 100 200 300 400 500

Dailyweightgain(g

/fish)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Temp 220C

Temp 240C

Temp 260C

Temp 290C

Figure 5: Daily weight gain of tilapia for sizes between 20 and 400g at varioustemperatures.

The equation defining the relationship between daily weight gain, fish size as well astemperature appears below.

Weight gain (g) = 0.0113 BW (g) 0.547 exp 0.090 Temp (13)

For W = Weight (g) of fish for weights between 20 and 400 g.T = Temperature between 22 - 290C

By rearranging this equation we can also predict the weight of fish after t days (W t)given the initial weight W0 at t0.

Wt = [W00.453 + 0.00512 exp 0.090 Temp days] 2.207 (14)

The daily feed intake depending on fish size and temperature can be described withthe same general equation:

Feed intake (g) = 0.0156 BW (g) 0.600 exp 0.085 Temp (15)

3.2.2 Composition of weight gain

An additional goal was to determine changes in body composition of fish relative totheir weight or age. Results of the analysis of the whole body composition of tilapiaatvarious sizes (3 450 g) including results from former trials are plotted for protein,lipid, moisture and energy in Figure 6. As it is obvious from Figure 6 no largechanges in energy and lipid content relative to fish size can be observed. This is in


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contrast to other fish species where lipid and energy increase significantly withincreasing fish weight while moisture decreases.

The following values describe the composition of tilapia for increasing weights alongthe growth cycle.

Protein (%) = 16.02 0.56 (mean std)

Ash (%) = 4.28 0.42 (mean std)

Energy (kJ / g) = 5.98 BW (g) 0.041 (16)

Lipid (%) = 5.87 BW (g) 0.095 (17)

Moisture (%) = 75.40 BW (g) -0.016 (18)

Where BW = body weight in g

Fish size

0 100 200 300 400 500

Composition(g/100gfish)

0

10

20

30

40

50

60

70

80

90

100

Energycontent(kJ/gfish)

0

2

4

6

8

10

12

14

16

Moisture Energy LipidProtein

Figure 6: Body composition of tilapia at increasing sizes


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4. Practical Applications

The results of this study provide us with the tools to quantify the daily protein andenergy needs of tilapia at any fish size within the water temperatures of 22 - 29C ascalculated in Table 7.

Table 7: Recommendations for supply of digestible energy (DE) and digestible

protein (DP) to tilapia grown at two different water temperatures (230C and 28C)

Body weight, per fish 50g 250g 400g

Water temperature 230C 280C 230C 280C 230C 280CWeight gaina, g / day 0.76 1.19 1.84 2.88 2.37 3.72

Energy requirement, kJ / fish / dayMetabolic BW, kg0.80 0.091 0.091 0.330 0.330 0.480 0.480

DEmaintb, 3.73 5.32 13.53 19.27 19.71 28.07

Energy gainc 5.34 8.38 13.76 21.58 18.15 28.46DEgrowth

d, 8.60 13.49 22.16 34.75 29.22 45.82DEmaint+growth

e 12.33 18.81 35.69 54.02 48.93 73.89Protein requirement, g / fish / dayMetabolic BW, kg0.70 0.123 0.123 0.379 0.379 0.527 0.527DPmaint

f, 0.058 0.087 0.178 0.269 0.247 0.374Protein gaing 0.121 0.191 0.377 0.461 0.380 0.596DPgrowth

h, 0.259 0.407 0.804 0.982 0.810 1.270DPmaint+growth

i, 0.317 0.494 0.626 1.251 1.057 1.644

a Predicted weight gain for tilapia at 23C respectively 280C , equation (13)b

Digestible energy required for maintenance = (- 39.02 + 3.48 T0

C) BW (kg)0.80

c Expected energy gain = weight gain energy content of gain, equation (16)d Digestible energy required for growth = expected energy gain 1.61 (or 1 / 0.62 -cost in units of DE to deposit one unit of energy as growth)e Total DE required for maintenance and growthfDigestible protein required for maintenance = (- 0.634 + 0.048 T 0C) BW (kg)0.70g Expected protein gain = weight gain protein content of gain (160 mg/ g)h Digestible protein required for growth = expected protein gain 2.13 (or 1 / 0.47 -cost in units of DP to deposit one unit of protein as growth).i Total DP required for maintenance and growth

The absolute daily protein requirement per fish is dependent on fish size and weightgain, regardless of DE content. Therefore, as demonstrated in Table 8, the proteinlevel expressed as a percentage of the feed will change according to the selected DEcontent of 12 or 16 MJ /kg. Omnivorous fish like the tilapia could thus be fed lowerenergy and protein diets assuming they are able to consume all the feed to acquirethe energy and protein needed for maximum growth. In this case the FCR would begreater as shown in Table 8.


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Table 8: Feed formulations including required feed intake for growing tilapia (at280C), when preparing feeds alternatively with predetermined energy or proteincontents.

Body weight, per fish 50g 250g 400g

Weight gaina, g /day 1.19 2.88 3.72Feed intakeb, g /day 1.76 4.63 6.14DE needc, kJ /fish/day 18.81 54.02 73.89DP needc, g/fish /day 0.494 1.251 1.644

DE content of feed 12 MJ 16 MJ 12 MJ 16 MJ 12 MJ 16 MJRequired feed intake,g/ fish/ day

1.57 1.18 4.50 3.38 6.16 4.62

Resulting DP content,g / kg

315 419 278 370 267 356

FCR 1.32 0.99 1.56 1.17 1.65 1.24

DP content of feed 250g 350g 250g 350g 250g 350gRequired feed intake,g /fish/day

1.97 1.41 5.00 3.57 6.58 4.70

FCR 1.65 1.18 1.74 1.24 1.77 1.26DP/DE ratio in feed,g / MJ

26.2 26.2 23.1 23.1 22.2 22.2

a Predicted weight gain for tilapia at 28C , equation (13)b Predicted voluntary feed intake at 28oC, equation (15)c see Table 7

Combining these protein and energy needs with digestibility data on locally availablefeed ingredients then allows us to formulate feeds and set up proper feeding tables asdemonstrated in Tables 9 and 10.

Table 9: Proposed diet formulation (per kg feed) and corresponding practical feeding

table for tilapia during the whole growing period (at 28C).

Weightrange (g)

Feed composition Weight gaing /fish/day

Feed intakeg /fish/day

Days ofgrowth

FCR

10 - 50 400 g CP*, 18 MJ GE*

50 g Lipid

0.83 1.00 48 1.20

50 - 100 370 g CP, 18 MJ GE,50 g Lipid

1.47 1.96 34 1.33

100 - 200 350 g CP, 18 MJ GE,50 g Lipid

2.13 3.07 47 1.44

200 - 300 350 g CP, 18 MJ GE,50 g Lipid

2.86 4.24 35 1.48

300 - 400 320 g CP, 18 MJ GE,50 g Lipid

3.45 5.58 29 1.62

* assuming digestibility of protein of 85% and of energy between 70 and 75%depending upon source (carbohydrate or lipid)


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Table 10: Proposed feeding table for tilapia at various temperatures ( in % feed ratioof biomass per day)

Water temperature 20-220C 22-240C 24-260C 26-280C 28-300C

Fish size

g

Protein content

of kg feed*10-25 400g 2.62 3.15 3.79 4.52 5.37

25-50 400g 1.83 2.20 2.64 3.15 3.74

50-75 370g 1.54 1.86 2.23 2.67 3.16

75-100 370g 1.33 1.60 1.92 2.29 2.72

100-150 350g 1.22 1.47 1.76 2.10 2.49

150-200 350g 1.06 1.28 1.52 1.81 2.14

200-300 350g 0.95 1.14 1.35 1.60 1.88

300-400 320g 0.87 1.04 1.25 1.48 1.75

400-500 300g 0.82 0.99 1.19 1.42 1.68

*

According to the formulations specified in Table 9

Using this approach to quantifying energy and protein demands in tilapia, it is thuspossible to calculate the biological and economical efficiency of different feeds andoptimize the feeding regime for various culture systems.

Optimization of Practical Feeds in Ti La Pia Farming- Israel

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